Theoretical tissue compartment inert gas pressures during a deep dive with and without deep decompression stops: a case analysis.

BACKGROUND Deep decompression stops are increasingly common in recreational technical diving. Concerns exist that they shift decompression stress back into slower tissues. A diver recorded an exceptional exposure dive, with deeps stops, on a commercially available dive computer. MATERIAL AND METHODS Using the R package SCUBA tissue inert gas pressures in 17 Bühlmann (ZH-L16A) compartments were estimated from the dive computer recorded profile. The RGBM dive plan generated by the diver's software was similarly interrogated, as was a third profile with reduced deep stops generated using the VPM-B/E model. RESULTS In this dive the combination of 5 gas switches appeared to ameliorate the effect of deep stops from 76 m depth. CONCLUSIONS A higher-than-anticipated inert gas content in a decompression mixture, coupled with climbing 200 stairs post-decompression, appear possible risk factors for decompression sickness. Nonetheless, the physiological effect of deep decompression stops during exceptional exposure, even when diving with gas switches, remains urgently to be determined to improve safe decompression following exceptional exposures. Until algorithms utilising deep decompression stops are validated with human data, dive profiles incorporating deep decompression stops should be considered experimental.